Question: Jessica is 2 times as old as Tiffany. 28 years ago, Jessica was 6 times as old as Tiffany. How old is Tiffany now?
Answer: We can use the given information to write down two equations that describe the ages of Jessica and Tiffany. Let Jessica's current age be $j$ and Tiffany's current age be $t$ The information in the first sentence can be expressed in the following equation: $j = 2t$ 28 years ago, Jessica was $j - 28$ years old, and Tiffany was $t - 28$ years old. The information in the second sentence can be expressed in the following equation: $j - 28 = 6(t - 28)$ Now we have two independent equations, and we can solve for our two unknowns. Because we are looking for $t$ , it might be easiest to use our first equation for $j$ and substitute it into our second equation. Our first equation is: $j = 2t$ . Substituting this into our second equation, we get: $2t$ $-$ $28 = 6(t - 28)$ which combines the information about $t$ from both of our original equations. Simplifying the right side of this equation, we get: $2 t - 28 = 6 t - 168$ Solving for $t$ , we get: $4 t = 140.$ $t = 35$.